Waste product tests are a group of blood tests that measure the levels of specific waste products (natural byproducts of metabolism) in the blood. An abnormal waste product test can signal such conditions as heart failure or kidney failure.

Before a waste product test, patients are usually ordered to fast for four to eight hours. They may also be ordered to reduce or stop taking some of their medications or vitamins because some substances can interfere with the results of the test. Patients must inform their physician of all medications and vitamins that are currently being taken.